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Lion conservation Give them land, lots of land under starry skies above - then fence them in.

That is the way to save Africa's wild lion population from near extinction, according to an international team of conservationists writing in the latest edition of Ecology Letters.

The team, including Australian researchers, says wild populations of African lion could decline to near extinction levels during the next 20-40 years.

However their work shows in fenced reserves in southern African, such as Kruger National Park, populations of lions are expected to remain at their potential capacity for the next 100 years.

Co-author Professor Stephen Garnett, an expert in conservation management at Charles Darwin University admits the idea of fencing large African reserves runs counter to a long-standing conservation practices.

Glorified zoo

"Lions are a casualty of unending human population growth and demand for resources," he says. "It is unlikely that this will change soon.

"The question is whether we decide to abdicate on wild, unmanaged populations of large animals and move into the 'zoo mode' where we keep them in zoos in the wealthy countries, and inside fences in Africa, and show videos of them to our grandchildren.

"This will work but it is a decision that is difficult for a biologist to be happy with."

"It is a natural environment inside a fence - is that a zoo? It's a very blurred zone."

He says the lions also play a key role in maintaining the ecosystem so it is important they are saved across the African continent.

"Having parks without large predators means you can destabilise the whole system," he says.

Costly operation

The new study shows while initial costs of building fences is high - about $3000 per kilometre - lions can be maintained at 80 per cent of their potential densities for $500 per square kilometre annually.

This compares with more than $2000 per square kilometre per year to maintain just 50 per cent of potential densities in unfenced populations.

Garnett says western nations should be prepared to pay the bulk of these lion management costs as it is predominantly western nations "that consume the pleasure of having lions in the wild".

Krebs says the importance of the study is it highlights that "conservation costs money and the larger the animal, the greater the cost".

"Conservation biologists can only make their best guesses of what might happen in the future, and what actions we might take as a society to prevent species loss," he says.

"It is up to each individual country to decide what it can do or wishes to do and the aggregate result will perhaps be undesirable for conservation."